Process for making metallic tungsten



% UNITED; ST ES .xon Amow, on'roxzo 1m, Jenn, AssIoNon-ro mrsonrsnr xooro musnnu, man, or rem, JAPAN, A. oonromrron or Jamar;

rmcn'ss non o maranuc won.

no Drawing. Application filed my a, me, Serial in. 120,532, imam Japan m 10, me.

This invention relates to a process of making technically pure metallic tungsten by treatingwith alkali or, alkaline solution the impure metallic tungsten which is prepared b reduction of impure tungsten oxide. The object of the invention is to make pure metallic tungsten easily and economically from all kinds of material containing tungsten.

In order to obtain pure metallic tungsten from the substances containing tungsten, it has hitherto been necessary first to make pure tungsten oxide. This has been done either in the alkali process or the acid process 1n the following way In the ordina alkali process, the tungsten ore or other so stance containing tungsten is treated first with alkali to convert tungsten into soluble alkali tungstate, which is thendecomposed by acid in order to obtain insoluble tun ten oxide. In this case, sillca, alumina an tin oxide which, are present 1n the ori 'nal material as impurities consume alkali and acid during the treatment in just the same way as tungsten does and contamlnate the resulting tungstate, and it is articularly difiicult to get rid of silica in t e precipitated oxide of tungsten. It was therefore absolutely necessary, for the purpose of making pure tungsten, to remove these 1mpurities either by preliminary mechanical or hysical treatment of the raw material or y purifying the alkali tungstate so that the precipitated tun sten omde may remain free from these admixtures, when the tungstate is decomposed-by acid. a

In the acid process theimpurities such as alumina, silica, tin oxide have to be removed from the raw material by physical or mechanical means before it is treated with acid, to obtain the tungsten oxide free from these impurities.

t any rate the tungsten oxide shows similar chemical reactions as silica and tin oxide when treated either with alkali or acid, andtherefore can be separated with a great deal of difiiculty, giving rise tothe waste of chemicals and labor in the course of separation and finally giving a poor yield of tungsten.

I have now found that metallic tungsten is not acted upon by al kali under. certain conditions, while silica, alumina and tin are acted upon under the same conditions. I have further found that technically. puretungsten can be made more easily and more economically by treating with alkali such impure. tungsten, metal as obtained from crude tungsten oxide or material, than by first purifying the startmg substance or intermediate product, i. e. raw tungsten oxide. The followin is an example of carrying my invention into prac-' from impure raw the crude metallic tungsten thusobtained are heated in an autoclave with 100 parts of 15% caustic soda solution at 150 C. for half an hour. The imfiurities which are present 1n the crude meta ic tungsten such as silica, alumina, or metallic tin, are dissolved by alkali under this condition, while the metallic tungsten remains intact and can be obtained in techmcall pure state after washing with water. In t is way we can obtain metallic tungsten of 99.5% purity fro crude metal containing 85.3% tungsten, 10.2% silica, 0.12% alumina, 0.5% tin, 3.0% tungsten oxide.

It will be obvious from the foregoing that, because of the high temperature maintained in the autoclave, a pressure considerably above atmospheric is developed and maintained during the treatment.

Example 2.Onc hundred parts of finely powdered scheelite are heated with 500 parts of 15% (by weight) hydrochloric acid at 100 C. for one hour. The decomposition product is well washed, dehydrated and reduced at 1200 C. The crude metallic tungsten thus formed is heated in an adequate vessel with equal weight of 20% caustic soda solution at 100 C. for one hour and a half. The impurities present in the crude metal go into solution as will be seen from the follow- 120 C. for one hour. By this means metallic tun sten of 98.5% purity is obtained from cru e metal containing 72.0% W, 8.7% SiO,, 12.3% Sn and 2.5% tungsten oxide.

In all of the above examlples, the purification is carried out, as wil be readily seen, under non-oxidizing conditions.

I however do not wish to limit in self to the above examples, as the ratio 0 alkali, its concentration, the temperature and duration of heating can be changed in a wide range without affecting the result aimed at. It is also eas to attaln the same object by using solid a kali instead of its'aqueous solution, i. e., b fusing or roasting with alkali in a non-oxidizing atmos here.

Having now particu arly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

1. A process of treating crude metallic tungsten to obtain technically pure tungsten therefrom, which consists in heating the crude metallic tungsten with an aqueous solution of alkali in a closed vessel under pres sure.

2. A process of producing technically. pure tungsten, which consists in decomposing a substance containing tungsten with inorganic acid and then reducing the crude oxide of tun ten thus formed to metal and purifying t 0 resulting crude metallic tungsten by heating the same with alkali.

3. A process of producing technically ure tungsten, which consists in decomposmg asubstance containing tungsten with inorganic acid in a closed vessel and then reducin the crude oxide of tungsten thus form to metal and purifying the resulting crude metallic tungsten by heating the same with alkali.

4. A process of producing technically pure tungsten, which consists in decomposmg a substance containing tungsten with inorganic acid in a closed vessel under pressure and then reducing the crude oxide of tungsten thus formed to metal and purifying the resulting crude metallic tungsten by heating the same with alkali.

' In testimony whereof I have afixed my signature.

KOJ I ANJ OW. v 

